Anatomical and molecular similarities suggest these two groups are close evolutionary relatives; together, they form the fowl clade which is scientifically known as Galloanserae or Galloanseres (initially termed Galloanseri) (Latin gallus ("rooster") + ānser ("goose")).

[9] Fossils such as Vegavis indicate that essentially modern waterfowl, albeit belonging to a now-extinct lineage, were contemporaries of the non-avian dinosaurs.

As opposed to the morphologically fairly conservative Galliformes, the Anseriformes have adapted to filter-feeding and are characterized by many autapomorphies related to this lifestyle.

[10][11] However, as strong support for the Galloanserae has emerged in subsequent studies, the fowl clade continues to be accepted as a genuine evolutionary lineage by the vast majority of scientists.

Pheasants have been widely introduced and naturalized outside of their native range in Asia to Europe and North America for use as food and sport.